Heat is thermal energy transferred from one object to another because of a difference in

Due to "Temperature" difference heat is transferred from "one object" to "another object".

Explanation:

In general there are three ways for heat to be transferred: Conduction (heat is transferred by vibration of particles), Convection (heat is transferred by movement of particles) & Radiation (heat is transferred in Infrared waves). Heat is also called as thermal energy which acts as kinetic energy when energy is given to atoms, molecules, ions in solids, liquids and gases due to which movement takes place. As heat flows from higher temperature to lower temperature and heat content "Q" of an object depend upon its specific heat "c" and its mass "m". For example when ice cube is added to room temperature water then transfer of heat energy will take place due to which ice melts in water and both of them reach to a common temperature which is also called as "Thermal Equilibrium" phase.